Metal pad modification

ABSTRACT

The present invention provides a structure. In an exemplary embodiment, the structure includes a base material, at least one metal pad, where a first surface of the metal pad is in contact with the base material, and a metal pedestal, where the metal pedestal is in contact with the metal pad, where a radial alignment of the metal pad is shifted by an offset distance, with respect to the metal pedestal, such that the metal pad is shifted towards a center axis of the base material, where a first dimension of the metal pad is smaller than a second dimension of the metal pad, where the second dimension is orthogonal to a line running from a center of the metal pad to the center axis of the base material, where the first dimension is parallel to the line.

BACKGROUND

The present disclosure relates to integrated circuit chips, and morespecifically, to metal pad modification.

SUMMARY

The present invention provides a structure. In an exemplary embodiment,the structure includes a base material, at least one metal pad, where afirst surface of the metal pad is in contact with a surface of the basematerial, a metal pedestal, where a first surface of the metal pedestalis in contact with a second surface of the metal pad, where a radialalignment of the metal pad is shifted by an offset distance, withrespect to the metal pedestal, such that the metal pad is shiftedtowards a center axis of the base material, where a first dimension ofthe metal pad is smaller than a second dimension of the metal pad, wherethe second dimension is orthogonal to a line running from a center ofthe metal pad to the center axis of the base material, where the firstdimension is parallel to the line running from the center of the metalpad to the center axis of the base material, and a solder bump incontact with a second surface of the metal pedestal.

In an exemplary embodiment, the structure includes a base material, atleast one metal pad, where a first surface of the metal pad is incontact with a surface of the base material, a metal pedestal, where afirst surface of the metal pedestal is in contact with a second surfaceof the metal pad, where a radial alignment of the metal pad is shiftedby an offset distance, with respect to the metal pedestal, such that themetal pad is shifted towards a center axis of the base material, and asolder bump in contact with a second surface of the metal pedestal.

In an exemplary embodiment, the structure includes a base material, atleast one metal pad, where a first surface of the metal pad is incontact with a surface of the base material, a metal pedestal, where afirst surface of the metal pedestal is in contact with a second surfaceof the metal pad, where a first dimension of the metal pad is smallerthan a second dimension of the metal pad, where the second dimension isorthogonal to a line running from a center of the metal pad to thecenter axis of the base material, where the first dimension is parallelto the line running from the center of the metal pad to the center axisof the base material, and a solder bump in contact with a second surfaceof the metal pedestal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 2 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 3 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 4 depicts a bar graph in accordance with an exemplary embodiment ofthe present invention.

FIG. 5 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 6 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 7 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 8 depicts a bar graph in accordance with an exemplary embodiment ofthe present invention.

FIG. 9 is a diagram depicting a design process used in semiconductordesign, manufacture.

DETAILED DESCRIPTION

The present invention provides a structure. In an exemplary embodiment,the structure includes a base material, at least one metal pad, where afirst surface of the metal pad is in contact with a surface of the basematerial, a metal pedestal, where a first surface of the metal pedestalis in contact with a second surface of the metal pad, where a radialalignment of the metal pad is shifted by an offset distance, withrespect to the metal pedestal, such that the metal pad is shiftedtowards a center axis of the base material, where a first dimension ofthe metal pad is smaller than a second dimension of the metal pad, wherethe second dimension is orthogonal to a line running from a center ofthe metal pad to the center axis of the base material, where the firstdimension is parallel to the line running from the center of the metalpad to the center axis of the base material, and a solder bump incontact with a second surface of the metal pedestal. In an embodiment,the line running from a center of the metal pad to the center axis ofthe base material is not an actual line but a constructive line usedonly for reference.

In an exemplary embodiment, the structure includes a base material, atleast one metal pad, where a first surface of the metal pad is incontact with a surface of the base material, a metal pedestal, where afirst surface of the metal pedestal is in contact with a second surfaceof the metal pad, where a radial alignment of the metal pad is shiftedby an offset distance, with respect to the metal pedestal, such that themetal pad is shifted towards a center axis of the base material, and asolder bump in contact with a second surface of the metal pedestal.

In an exemplary embodiment, the structure includes a base material, atleast one metal pad, where a first surface of the metal pad is incontact with a surface of the base material, a metal pedestal, where afirst surface of the metal pedestal is in contact with a second surfaceof the metal pad, where a first dimension of the metal pad is smallerthan a second dimension of the metal pad, where the second dimension isorthogonal to a line running from a center of the metal pad to thecenter axis of the base material, where the first dimension is parallelto the line running from the center of the metal pad to the center axisof the base material, and a solder bump in contact with a second surfaceof the metal pedestal.

One of the major reliability concerns of current and next generationintegrated circuits is mechanical failure due to stresses induced by thechip-package interactions (CPI). The packaged integrated circuits aresubjected to thermal-mechanical stresses due to a mismatch of thecoefficient of thermal expansion of the silicon, lead-free controlledcollapse chip connection (C4) bumps, and the organic flip-chip substrateleading to mechanical delamination or cracking in the weakerlow-k/ultra-low K (ULK) films within the chip. Aluminum pads or metalpads in the back-end-of-line (BEOL) can lead to high levels of CPIstress within the weak low-k and ultra-low k BEOL levels. In anembodiment of the present invention, offsetting the metal pad reducesCPI stresses in the weaker BEOL levels. In an embodiment of the presentinvention, an oblong metal pad reduces CPI stresses in the weaker BEOLlevels.

The decreasing feature sizes and increasing power/current andperformance requirements of the current and next generation integratedcircuit devices has led to a need for materials changes in the chipresulting in weaker low-k and ultra low-k films (ULK), increases in thenumber of fine pitch Cu wiring levels, and use of more stressful underbump metallurgy (UBM)/lead-free C4 bumps and organic laminates [1-2].All of these contribute to a weaker and highly stressed packaged partsusceptible to white C4 bumps due to failure in the BEOL regions of thechip during the assembly or chip-join processing and/or duringreliability stressing of the parts. White C4 bumps are C4 bumps thathave cracks in the chip metallurgy under the C4 bumps.

The thermal mechanical stresses that are generated in the packaged partduring the chip-join reflow process are driven by the mismatch of thecoefficient of thermal expansion of the chip, the lead-free solder, andthe organic flip-chip substrate, which leads to delaminations or cracksin the weaker low-k/ULK levels in the chip. These thermally inducedtensile stresses are typically worse at the chip edge than the chipcenter. Several factors can influence the stresses that arise due tochip-package interactions and the white bumps underneath the C4 joints.Factors such as materials properties (BEOL, C4, laminate), chip size,final passivation via design, size and thickness, solder bump and UBM(type, orientation, and dimensions), underfill type, chip-join profile,and laminate structure are a few of them. In an embodiment of thepresent invention, shifting a metal pad towards a center of a basematerial reduces failure due to tensile stress in a chip. In anembodiment of the present invention, modifying the shape of a metal padreduces failure due to tensile stress in a chip.

In an embodiment, shifting a metal pad towards the center of the basematerial or chip reduces peeling stress. In an embodiment, changing theaspect ratio of the metal pad such that the smaller of the twodimensions is in line with a line running substantially from the centerof a metal pad to the center of the base material or chip reducespeeling stress.

In an embodiment, the metal pad is connected to a base material. Thebase material is a multilayer electronic package. In an embodiment, thebase material comprises a material selected from the group consisting ofa photo sensitive polyimide material, an oxide material, and a nitridematerial. In an embodiment, the base material comprises a materialselected from the group consisting of a photo sensitive polyimidematerial, a silicon oxide material, and/or a silicon nitride materialdeposited on a silicon chip. In an embodiment, the metal pad is formedon a surface of the base material. In an embodiment, the metal pad isformed in a recess in the base material. In an embodiment, the metal padis deposited within the base material. In an embodiment, the metal padis an aluminum pad that has been deposited by sputtering orelectroplating. In an embodiment, the metal pad is deposited onto anarea of the base material with a metal via or metal component. The metalpad is conductively coupled to the metal filled via or metal component.In an embodiment, the metal pad comprises a material selected from thegroup consisting of gold, gold alloy, copper, copper alloy, aluminum,and aluminum alloy. In an embodiment, the metal pad is an aluminum pad.In an embodiment, the base material is a chip.

In an embodiment, a passivation layer is formed on the exposed portionof the base material and a portion of the metal pad. In example, oncethe metal pad is formed, the passivation layer may be deposited onto thesurface of the base material and the metal pad leaving a via or openregion on the metal pad with no passivation layer. In an embodiment,there is a passivation layer between the metal pedestal and the metalpad with a via in the passivation layer, and where the metal pedestalcontacts the metal pad through the via in the passivation layer. In anembodiment, the passivation layer is a dielectric passivation layer. Forexample, the passivation layer could be comprised of an organicmaterial, such as a polymer. The passivation layer could also becomprised of a photosensitive polyimide. In an embodiment, thepassivation layer has a thickness ranging from 0 μm to 20 μm.

In an embodiment, a metal pedestal is formed, at least partially, on thesurface of the metal pad. In an embodiment, the metal pedestal is alsoformed partially on a surface of the passivation layer. In anembodiment, the metal pedestal is partially formed on the surface of thebase material. In an embodiment, the metal pedestal comprises a materialselected from the group consisting of gold, gold alloy, copper, copperalloy, aluminum, aluminum alloy, titanium, and tantalum nitride. In anembodiment, the metal pedestal is deposited on the passivation layer andthe second surface of the metal pad. For example, the metal pedestal maybe deposited by electroless plating. In a further embodiment, theelectroless plating may be a seed layer and the metal pedestal may befurther deposited by electroplating.

In an embodiment, the metal pad is radially offset in regard to themetal pedestal. The metal pad is shifted towards a center axis of thebase material. The center axis of the base material is a line runningsubstantially perpendicular to the two largest flat surfaces of the basematerial. In an embodiment, the offset distance ranges from 0 μm to 20μm. The offset distance can be measured from a center axis of the metalpad to a center axis of the pedestal. In an embodiment, duringconstruction, the metal pad is deposited at an offset with reference towhere the metal pedestal will be placed. In an embodiment, the metalpedestal is offset from the center axis of the metal pad, where themetal pedestal is shifted away from a center axis of the base material.

In an embodiment, first dimension of the metal pad is smaller than asecond dimension of the metal pad, wherein the second dimension isorthogonal to a line running from a center of the metal pad to thecenter axis of the base material, wherein the first dimension isparallel a to line running from the center of the metal pad to thecenter axis of the base material. In an embodiment, the metal pad has across sectional shape selected from the group consisting of roundedrectangle, elliptical, and oblong. For example, the metal pad can be anypolygon or curve shape that has a face or cross section with onedimension larger than another. The cross-section does not need to besymmetrical. The cross-sectional shape could have any number of sides.In an embodiment, an aspect ratio of the second dimension to the firstdimension is greater than 1:1 and less than 2:1.

In an embodiment, a solder bump is formed on a surface of the metalpedestal. In an embodiment, the solder bump comprises a materialselected from the group consisting of leaded solder, lead free solder,bismuth based lead free solder, silver based lead free solder, copperbased lead free solder, and high lead core solder.

Metal Pad Offset

Referring to FIG. 1, in an embodiment, a metal pad 110 is deposited on abase material 120. A metal pedestal 140 is at least partially depositedon metal pad 110. An axis 160 of metal pad 110 is offset from an axis170 of metal pedestal 140 by an offset distance 165.

In an embodiment, base material 120 has one or more metal filled vias130 that are electrically connected to metal pad 110. In an embodiment,a passivation layer is formed on metal pad 110 and base material 120. Inan embodiment, metal pedestal 140 is formed on a passivation layer 190.In an embodiment, there is not a passivation layer. In an embodiment,metal pedestal 140 is a single coating deposited on metal pad 110 andpassivation layer 190. In an embodiment, metal pedestal 140 is a singlelayer deposited on metal pad 110 and base material 120. In anembodiment, metal pedestal 140 is deposited on a seed layer 150. In anembodiment, axis 160 is a center axis of metal pad 110. Axis 170 is acentral axis of metal pedestal 140. Metal pad 110 is shifted towards acenter of base material 120 in reference to metal pedestal 140. Theshift or offset of metal pad 110 is measured by offset distance 165. Forexample, passivation layer 190 could be an electrically inert materialthat could also be an oxygen barrier. In an embodiment, there is nopassivation layer. In an embodiment, a solder bump 180 is formed onmetal pedestal 140. In an embodiment, structure 100 is part of anelectrical component with multiple solder bonds configurations similarto those shown in structure 100. In an embodiment, the configurationsshown by structure 100 is used for the solder bonds closest to thecorners of the electrical component while others closer to the center ofthe component may have a different configuration. In an embodiment,structure 100 is part of a chip.

Referring to FIG. 2, in an embodiment, a metal pedestal 240 is firstdeposited with a thin seed layer of metal and then a thicker layer ofmetal is deposited on the seed layer. In an embodiment, a passivationlayer 250, is deposited on a base material 220 and a metal pad 210 witha via 255 in passivation layer 250. In an embodiment, metal pedestal 240is deposited on metal pad 210 and passivation layer 250, where metalpedestal 240 is in electrical contact with metal pad 210. In anembodiment, there is a passivation layer above base material 220 andsurrounding metal pedestal 240. In an embodiment, there is nopassivation layer. In an embodiment, a solder bump 280 is formed onmetal pedestal 240. In an embodiment, metal pad 210 is offset by anoffset distance 265, where offset distance 265 is the distance from acentral axis 270 of the metal pedestal to a central axis 260 of themetal pad 210. In an embodiment, structure 200 is part of an electricalcomponent with multiple solder bonds configurations similar to thoseshown in structure 200. In an embodiment, the configurations shown bystructure 200 are used for the solder bonds closest to the corners ofthe electrical component while others closer to the center of thecomponent have a different configuration.

Referring to FIG. 3, view 300 is a transparent top down view of astructure according to an embodiment of the invention. In an embodiment,a metal pedestal 340, a via 355 in a passivation layer, and a solderbump 380 are all substantially centered on a common axis 370, and ametal pad 310 is shifted or offset towards a center of a base materialby an offset distance 365. In an example, offset distance 365 ismeasured from common axis 370 to a center axis 360 of metal pad 310. Inan embodiment, metal pad 310 is any regular polygon or curved shape. Forexample, the top surface/cross-sectional view of metal pad 310 is shownto be a hexagon, but it could also be a circle square or octagon.

Metal Pad Shape

Referring to FIG. 5, in an embodiment, a metal pad 510 is deposited on abase material 520. A metal pedestal 540 is at least partially depositedon metal pad 510.

In an embodiment, base material 520 has one or more metal filled vias530 that are electrically connected to metal pad 510. In an embodiment,a passivation layer 590 is formed on metal pad 510 and base material520. In an embodiment, metal pedestal 540 and 550 is formed on apassivation layer 590. In an embodiment, there is not a passivationlayer 590. In an embodiment, metal pedestal 540 and 550 are two coatingsdeposited on metal pad 510 and passivation layer 590. In an embodiment,metal pedestal 540 and 550 are two coatings that are deposited on metalpad 510 and base material 520.

In an embodiment, axis 560 is, substantially, a central axis of metalpad 510 and metal pedestal 540. In an embodiment, passivation layer 590is partially deposited on metal pad 510. For example, passivation layercould be an electrically inert material that could also be an oxygenbarrier. In an embodiment, there is no passivation layer. In anembodiment, a solder bump 580 is formed on metal pedestal 540. In anembodiment, metal pad 510 has a first dimension that is longer than asecond dimension, such that a line running parallel to the firstdimension would substantially point towards the center of base material520. In an embodiment, structure 500 is part of an electrical componentwith multiple solder bonds configurations similar to those shown instructure 500. In an embodiment, the configurations shown by structure500 is used for the solder bonds closest to the corners of theelectrical component while others closer to the center of the componentmay have a different configuration.

Referring to FIG. 6, in an embodiment, a metal pedestal 640 is firstdeposited with a thin seed layer of metal 650 and then a thicker layerof metal is deposited on seed layer 650. In an embodiment, a passivationlayer 690 is deposited on a base material 620 with a via 630 and a metalpad 610. In an embodiment, a passivation layer 690 is deposited on ametal pad 610. In an embodiment, metal pedestal 640 is deposited onmetal pad 610 and passivation layer 690, where metal pedestal 640 is inelectrical contact with metal pad 610. In an embodiment, there is apassivation layer 690 above base material 620 and surrounding the metalpedestal. In an embodiment, a solder bump 680 is formed on metalpedestal 640. In an embodiment, metal pedestal 640 and metal pad 610 arecentered around axis 660. In an embodiment, structure 600 is part of anelectrical component with multiple solder bonds configurations similarto those shown in structure 600. In an embodiment, the configurationsshown by structure 600 is used for the solder bonds closest to thecorners of the electrical component while others closer to the center ofthe component may have a different configuration.

Referring to FIG. 7, view 700 is a transparent top down view of thestructure according to an embodiment of the invention. In an embodiment,a metal pedestal 740, a via 755 in a passivation layer, a solder bump,and a metal pad 710 are all substantially centered on common axis 760.In an embodiment, metal pad 710 would be shifted towards a center ofbase material 720. In an embodiment, metal pad 710 is any regularpolygon or curved shape with a first dimension 761 that is shorter thana second dimension 776. For example, the top surface/cross-sectionalview of metal pad 710 is shown to be an octagon, but it could also be asquare with rounded corners or an oblong octagon. In an embodiment,first dimension 761 of metal pad 710 is smaller than second dimension776 of metal pad 710, where second dimension 776 is substantiallyorthogonal to a line running through the center of metal pad 710 and thecenter axis of base material 720, wherein first dimension 761 issubstantially parallel to line running through the center of metal pad710 and the center axis of base material 720.

In an embodiment, each of FIG. 1-3 and FIG. 5-7 depict one section of alarger structure. For example, an array of the structures where each ofview 100, 200, 300, 500, 600, and 700 could be one structure in such anarray.

Some embodiments of the present disclosure are shown in FIG. 1-3 andFIG. 5-7. In an exemplary embodiment, the structure includes a basematerial 120, 220, 520, and 620, at least one metal pad 110, 210, 310,510, 610, and 710, where a first surface of metal pad 110, 210, 310,510, 610, and 710 is in contact with a surface of base material 120,220, 520, and 620. The structure has a first surface of a metal pedestal150, 140, 250, 240, 340, 550, 540, 650, 640, and 740 is in contact witha second surface of metal pad 110, 210, 310, 510, 610, and 710. In thestructure, radial alignment of metal pad 110, 210, 310, 510, 610, and710 is shifted by an offset distance 165, 265, and 365, with respect tometal pedestal 150, 140, 250, 240, and 340, such that metal pad 110,210, and 310 is shifted towards a center axis of base material 120 and220. For example, the center axis 160, 260, and 360 of metal pad 110,210, and 310 is offset from the center axis 170, 270, and 370 of metalpedestal 150, 140, 250, 240, and 340 by the offset distance. Regardingmetal pad 110, 210, 310, 510, 610, and 710, a first dimension 761 ofmetal pad 110, 210, 310, 510, 610, and 710 is smaller than a seconddimension 776 of metal pad 110, 210, 310, 510, 610, and 710, where thesecond dimension 776 of metal pad 110, 210, 310, 510, 610, and 710 is afirst line 777 orthogonal to a line running from a center 160, 260, and360 of metal pad 110, 210, 310, 510, 610, and 710 to the center axis ofbase material 120 and 220, and the first dimension 761 of metal pad 110,210, 310, 510, 610, and 710 is a line 762 parallel to the line runningfrom the center of metal pad 110, 210, 310, 510, 610, and 710 to thecenter axis of base material 120 and 220. The structure has a solderbump 180, 280, 380, 580, 680, and 780 in contact with a second surfaceof metal pedestal 150, 140, 250, 240, and 340.

In an embodiment, a method for producing a bonding structure including,forming a base material 120, 220, 520, and 620, depositing at least onemetal pad 110, 210, 310, 510, 610, and 710 on base material 120, 220,520, and 620, where a first surface of metal pad 110, 210, 310, 510,610, and 710 is in contact with a surface of base material 120, 220,520, and 620, depositing a metal pedestal 150, 140, 250, 240, 340, 550,540, 650, 640, and 740 on the structure, where a first surface of metalpedestal 150, 140, 250, 240, 340, 550, 540, 650, 640, and 740 is incontact with a second surface of metal pad 110, 210, 310, 510, 610, and710, where a radial alignment of metal pad 110, 210, 310, 510, 610, and710 is shifted by an offset distance 165, 265, and 365, with respect tometal pedestal 150, 140, 250, 240, 340, 550, 540, 650, 640, and 740,such that metal pad 110, 210, 310, 510, 610, and 710 is shifted towardsa center axis of base material 120, 220, 520, and 620, where a firstdimension 761 of metal pad 110, 210, 310, 510, 610, and 710 is smallerthan a second dimension 776 of metal pad 110, 210, 310, 510, 610, and710, where the second dimension 776 is orthogonal to a line running froma center of metal pad 110, 210, 310, 510, 610, and 710 to the centeraxis of base material 120, 220, 520, and 620, where first dimension 761is parallel to the line running from the center of metal pad 110, 210,310, 510, 610, and 710 to the center axis of base material 120, 220,520, and 620, and depositing a solder bump 180, 280, 380, 580, 680, and780 on the structure in contact with a second surface of metal pedestal150, 140, 250, 240, 340, 550, 540, 650, 640, and 740.

In an exemplary embodiment, the structure includes a base material 120,220, 520, and 620, at least one metal pad 110, 210, 310, 510, 610, and710, where a first surface of metal pad 110, 210, 310, 510, 610, and 710is in contact with a surface of base material 120, 220, 520, and 620.The structure has a first surface of a metal pedestal 150, 140, 250,240, 340, 550, 540, 650, 640, and 740 is in contact with a secondsurface of metal pad 110, 210, 310, 510, 610, and 710. In the structure,radial alignment of metal pad 110, 210, 310, 510, 610, and 710 isshifted by an offset distance 165, 265, and 365, with respect to metalpedestal 150, 140, 250, 240, and 340, such that metal pad 110, 210, and310 is shifted towards a center axis of base material 120 and 220. Forexample, the center axis 160, 260, and 360 of metal pad 110, 210, and310 is offset from the center axis 170, 270, and 370 of metal pedestal150, 140, 250, 240, and 340 by the offset distance 165, 265, and 365.The structure has a solder bump 180, 280, 380, 580, 680, and 780 incontact with a second surface of metal pedestal 150, 140, 250, 240, and340.

In an exemplary embodiment, the structure includes a base material 120,220, 520, and 620, at least one metal pad 110, 210, 310, 510, 610, and710, where a first surface of metal pad 110, 210, 310, 510, 610, and 710is in contact with a surface of base material 120, 220, 520, and 620.The structure has a first surface of a metal pedestal 150, 140, 250,240, 340, 550, 540, 650, 640, and 740 is in contact with a secondsurface of metal pad 110, 210, 310, 510, 610, and 710. Regarding metalpad 110, 210, 310, 510, 610, and 710, a first dimension 761 of metal pad110, 210, 310, 510, 610, and 710 is smaller than a second dimension 776of metal pad 110, 210, 310, 510, 610, and 710, where the seconddimension 776 of metal pad 110, 210, 310, 510, 610, and 710 is a firstline 777 orthogonal to a line running from a center 160, 260, and 360 ofmetal pad 110, 210, 310, 510, 610, and 710 to the center axis of basematerial 120 and 220, and the first dimension 761 of metal pad 110, 210,310, 510, 610, and 710 is a line 762 parallel to the line running fromthe center of metal pad 110, 210, 310, 510, 610, and 710 to the centeraxis of base material 120 and 220. The structure has a solder bump 180,280, 380, 580, 680, and 780 in contact with a second surface of metalpedestal 150, 140, 250, 240, and 340.

In an embodiment, parallel means substantially parallel. For example,the range could be from −25° to 25° off of parallel. In an embodiment,orthogonal means substantially orthogonal. For example, the range couldbe from −25° to 25° off of orthogonal.

Examples

Referring to FIG. 4, using configurations similar to the embodimentsshown in FIG. 1-3, it has been observed that the stresses in the ULKlayers are sensitive to the metal pad offset distance 165, 265, and 365as shown in mechanical modeling results 400. According to embodiments ofthe present invention, the offset distance 165, 265, and 365 of metalpads was varied in a mechanical modeling simulation to determine theireffect on the ULK stresses. The variation of average ULK peeling stressas a function of relative metal pad offset distance 165, 265, and 365 isplotted in FIG. 4. In the plots, the ULK stresses in the y-axis and thepad offset distance 165, 265, and 365 in the x-axis have beennormalized. Hard dielectric thickness, final passivation (FV) viadiameter, metal pad size, metal pad thickness, and the UBM size wereheld constant for all cases modeled. Bar 410 shows no offset distance165, 265, and 365 resulted in an average peeling stress of 5.3 MPa. Theaverage peeling stress was reduced as the offset distance 165, 265, and365 towards a base material center was increased. The bars 420, 430, and440 show an average peeling stress of −2.0 MPa for an offset distance165, 265, and 365 of 1.6 μm, −7.7 MPa for an offset distance 165, 265,and 365 of 3.2 μm, and −17.9 MPa for an offset distance 165, 265, and365 of 4.7 μm.

Referring to FIG. 8, using configurations similar to the embodimentsshown in FIG. 5-7, it has been observed that the stresses in the ULKlayers are sensitive to the metal pad shape and orientation as shown inmechanical modeling results 800. Demonstrating embodiments, shapes ofmetal pads were varied in a mechanical modeling simulation to determinetheir effect on the ULK stresses. All orientations were held constant inthat smallest dimension 761 was roughly perpendicular to a line runningfrom the center of a base material to the center of the metal pad. Thevariation of an average ULK peeling stress as a function of relativeratio of the metal pad is plotted in FIG. 8. In the plots, the ULKstresses in the y-axis and the pad aspect ratio in the x-axis have beennormalized. Hard dielectric thickness, final passivation (FV) viadiameter, overall metal pad size, metal pad thickness, and the UBM sizewere held constant for all cases modeled. A square shape, depicted bybar 810, resulted in an average peeling stress of 5.3 MPa. The averagepeeling stress was reduced as an aspect ratio, with largest dimension776 perpendicular to a line running towards the center axis of the basematerial, was increased. Bars 820, 830, and 840 show an average peelingstress of 3.6 MPa for an aspect ratio of 1, −0.1 MPa for an aspect ratioof 1.6, and −1.3 for an aspect ratio of 2.

In an embodiment, the metal pad is offset toward the center axis of thebase material and has a shape such that a dimension roughly parallel toa line running from the center axis of the base material to a centeraxis of the metal pad is smaller than a dimension roughly perpendicularto a line running from the center axis of the base material to a centeraxis of the metal pad.

FIG. 9 is a diagram depicting a design process used in semiconductordesign, manufacture, and/or testing of structures depicted in FIG.1-FIG. 3 and FIG. 5-FIG. 7, according to embodiments consistent with thefigures.

FIG. 9 illustrates multiple design structures 900 including an inputdesign structure 920 that is preferably processed by a design process.Design structure 920 may be a logical simulation design structuregenerated and processed by design process 910 to produce a logicallyequivalent functional representation of a hardware device. Designstructure 920 may alternatively include data or program instructionsthat, when processed by design process 910, generate a functionalrepresentation of the physical structure of a hardware device. Whetherrepresenting functional or structural design features, design structure920 may be generated using electronic computer-aided design, such asthat implemented by a core developer/designer. When encoded on amachine-readable data transmission, gate array, or storage medium,design structure 920 may be accessed and processed by at least onehardware or software modules within design process 910 to simulate orotherwise functionally represent an electronic component, circuit,electronic or logic module, apparatus, device, or system such as thoseshown in FIG. 1-FIG. 3 and FIG. 5-FIG. 7. As such, design structure 920may include files or other data structures including human ormachine-readable source code, compiled structures, andcomputer-executable code structures that, when processed by a design orsimulation data processing system, functionally simulate or otherwiserepresent circuits or other levels of hardware logic design. Such datastructures may include hardware-description language design entities orother data structures conforming to or compatible with lower-level HDLdesign languages such, or higher-level design languages.

Design process 910 preferably employs and incorporates hardware orsoftware modules for synthesizing, translating, or otherwise processinga design/simulation functional equivalent of the components, circuits,devices, or logic structures shown in FIG. 1-FIG. 3 and FIG. 5-FIG. 7,to generate a description of the connectivity of an electronic circuit980 which may contain design structures such as design structure 920.Description of the connectivity of an electronic circuit 980 maycomprise, for example, compiled or otherwise processed data structuresrepresenting a list of wires, discrete components, logic gates, controlcircuits, I/O devices, models, etc. that describe the connections toother elements and circuits in an integrated circuit design. Descriptionof the connectivity of an electronic circuit 980 may be synthesizedusing an iterative process in which description of the connectivity ofan electronic circuit 980 is resynthesized at least one times dependingon design specifications and parameters for the device. As with otherdesign structure types described herein, description of the connectivityof an electronic circuit 980 may be recorded on a machine-readable datastorage medium or programmed into a programmable gate array. The storagemedium may be a non-volatile storage medium such as a magnetic oroptical disk drive, a programmable gate array, a compact flash, or otherflash memory. Additionally, the medium may be a system or cache memory,buffer space, or electrically or optically conductive devices andmaterials on which data packets may be transmitted and intermediatelystored through the internet, or other suitable networking means. As usedherein, a storage medium upon which a design structure, e.g., 900, 920,or 990, is stored is not to be construed as a transitory signal per se.

Design process 910 may include hardware and software modules forprocessing a variety of input data structure types including descriptionof the connectivity of an electronic circuit 980. Such data structuretypes may reside, for example, within library elements 930 and include aset of commonly used elements, circuits, and devices, including models,layouts, and symbolic representations, for a given manufacturingtechnology, e.g., different technology nodes, 32 nm, 45 nm, 90 nm, etc.The data structure types may further include design specifications 940,characterization data 950, verification data 960, design rules 970, andtest data files 985 which may include input test patterns, output testresults, and other testing information. Design process 910 may furtherinclude, for example, standard mechanical design processes such asstress analysis, thermal analysis, mechanical event simulation, processsimulation for operations such as casting, molding, and die pressforming, etc. One of ordinary skill in the art of mechanical design canappreciate the extent of possible mechanical design tools andapplications used in design process 910, without deviating from thescope and spirit of the disclosure. Design process 910 may also includemodules for performing standard circuit design processes such as timinganalysis, verification, design rule checking, place and routeoperations, etc.

Design process 910 employs and incorporates logic and physical designtools such as HDL compilers and simulation model build tools to processdesign structure 920 together with some or all of the depictedsupporting data structures, along with any additional mechanical designor data, to generate a second design structure 990. Design structure 990resides on a storage medium or programmable gate array in a data formatused for the exchange of data of mechanical devices and structures(e.g., any other suitable format for storing or rendering suchmechanical design structures). Similar to design structure 920, designstructure 990 preferably comprises at least one files, data structures,or other computer-encoded data or instructions that reside ontransmission or data storage media and that generate a logically orotherwise functionally equivalent form of at least one of theembodiments of the disclosure shown in FIG. 1-FIG. 3 and FIG. 5-FIG. 7.In one embodiment, design structure 990 may comprise a compiled,executable HDL simulation model that functionally simulates the devicesshown in FIG. 1-FIG. 3 and FIG. 5-FIG. 7.

Design structure 990 may also employ a data format used for the exchangeof layout data of integrated circuits and/or symbolic data format (e.g.,any other suitable format for storing such design data structures).Design structure 990 may comprise information such as symbolic data, mapfiles, test data files, design content files, manufacturing data, layoutparameters, wires, levels of metal, vias, shapes, data for routingthrough the manufacturing line, and any other data required by amanufacturer or other designer/developer to produce a device orstructure as described above and shown in FIG. 1-FIG. 3 and FIG. 5-FIG.7. Design structure 990 may then proceed to a state 995 where, forexample, design structure 990 proceeds to tape-out, is released tomanufacturing, is released to a mask house, is sent to another designhouse, is sent back to the customer, etc.

It will be understood that when an element is described as being“connected,” “deposited on,” or “coupled” to or with another element, itcan be directly connected or coupled to the other element or, instead,one or more intervening elements may be present.

The descriptions of the various embodiments of the present disclosurehave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A structure comprising: a base material; at leastone metal pad, wherein a first surface of the metal pad is in contactwith a surface of the base material, wherein the metal pad is depositedwithin the base material; a metal pedestal, wherein a first surface ofthe metal pedestal is in contact with a second surface of the metal pad,wherein a radial alignment of the metal pad is shifted by an offsetdistance, with respect to the metal pedestal, such that the metal pad isshifted towards a center axis of the base material, wherein the offsetdistance ranges from 0 μm to 20 μm, wherein a first dimension of themetal pad is smaller than a second dimension of the metal pad, whereinthe second dimension is orthogonal to a line running from a center ofthe metal pad to the center axis of the base material, wherein the firstdimension is parallel to the line running from the center of the metalpad to the center axis of the base material, wherein an aspect ratio ofthe second dimension to the first dimension is greater than 1:1 and lessthan 2:1; and a solder bump in contact with a second surface of themetal pedestal; a passivation layer between the metal pedestal and themetal pad with a via in the passivation layer, wherein the metalpedestal contacts the metal pad through the via in the passivationlayer, wherein the metal pedestal is deposited on the passivation layerand the second surface of the metal pad, wherein the passivation layerhas a thickness ranging from 0 μm to 20 μm.